# Positive and Negative pressure in a cigar room?



## Wookieefoot (Dec 26, 2007)

OK, I know I'm fresh fish and all, so I hope I'm posting in the right area.:hn Looked around and this seems like the right place, heh. 

I've been working on a 10x8 room in my finished basement. Turning it into my man cave/cigar room. I got tired of standing around in my non-heated garage for an hour+ in this chilly MN weather. Now there's no window in the room. So I'm installing a 130 CFM bath fan in the ceiling, I know its not much but I figure it should be fine with me being the only smoker in there. I'm also going to be using a Csonka Air Purifier. 

My problem is I don't totally understand the whole negative/positive air pressure dilemma. So if I have air being exhausted and don't introduce new air flow, what happens? Will all the air be sucked out of the room and I will slowly suffocate? ... J/K lol. 

Is it that big of a deal for such a small room? If I leave the bottom of the door unsealed would that be sufficient? I dunno, its starting to give me a headache and I knew I could get some answers or feedback from you guys. :cb


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## BillyCigars (Nov 17, 2007)

I don't have any advice for you, but I can't wait to see pictures of the finished man cave!!! :tu


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## [email protected] (Jun 25, 2007)

the only way that the air pressure would matter in such a room is if the room was 100% sealed. which is almost impossible to do. the only thing that could happen is if your fan pulls air out significantly faster than the fresh air is coming in you would burn your fan out. thats about it. you aren't going to suck yourself inside out or anything :r the fan would just stop working.

the air purifier should be plenty without the fan as long as its just you in there. the only time you should need the fan is if you have buddies over.

cant wait to see pics, i am working on turning my shed (roughly 10' x 10') into my man cave.


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## c2000 (Oct 16, 2003)

First of all welcome to the club,,as a fellow Minnesota smoker,,I do smoke in the garage and use a Big Buddy Propane heater and it gets the job done..I smoke a pipe in the garage but when I have a friend over for a cigar that odor is really tough to get out.. As far as your fan is concerned I don't think its big enough,,when you light up you will find out in a hurry . Regarding the air flow as long as you are putting a fan in you could also route a cold air intake tube like you have in your furnace room.. Having the ozoneator (Csonka) will help ,,just leave it on high after you leave the room..also burning a large candle will help get rid of the smoke..Let us know how everything works for you...

Jerry in Minnesota.


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## Da Klugs (Jan 8, 2005)

130 cfm is not a large amount of airflow smoke wise. It's probably enough for one smoker. If you have guests it will get hazy. The real issue is your HVAC. If there is a return air duct in your man cave.. it will suck smoke into your HVAC and spread it around the house. I have a 700 cfm fan in my office.. around 25 x 20. It creates "negative pressure" meaning air wants to flow into the room from any point.. cracks in walls, through the door (nice breeze), the cold air return as well as the intake vents from the furnace. But, when the furnace is running the returns go positive meaning that they suck air from my office back into the HVAC stinking up the rest of the office. This is a combination of the increased pressure being added by the HVAC intakes and the returns having more negative pressure at the duct point than the exhaust fan can generate for the entire space. If you have a return in your man cave you can test this by taping a plastic garbage bag around the return vent. with your fan on and the furnace off the bag should partially inflate into your man cave (negative pressure). Might not appear to be working much with a 130 cfm, if so, block the crack under the door and you should see it inflate.

Then turn the furnace on. If the bag deflates, you have positive pressure back into the HVAC.

My situation is unique in that I have a dedicated thermostat and furnace for just my and sams office so when smoking I turn it off to prevent the problem form occuring. The other furnaces keep running and the air that gets sucked into the office by the fan is either warm or cold depending on the season.

Anyhoo.. congrats on the man cave!


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## hova45 (Jun 17, 2007)

Da Klugs said:


> 130 cfm is not a large amount of airflow smoke wise. It's probably enough for one smoker. If you have guests it will get hazy. The real issue is your HVAC. If there is a return air duct in your man cave.. it will suck smoke into your HVAC and spread it around the house. I have a 700 cfm fan in my office.. around 25 x 20. It creates "negative pressure" meaning air wants to flow into the room from any point.. cracks in walls, through the door (nice breeze), the cold air return as well as the intake vents from the furnace. But, when the furnace is running the returns go positive meaning that they suck air from my office back into the HVAC stinking up the rest of the office. This is a combination of the increased pressure being added by the HVAC intakes and the returns having more negative pressure at the duct point than the exhaust fan can generate for the entire space. If you have a return in your man cave you can test this by taping a plastic garbage bag around the return vent. with your fan on and the furnace off the bag should partially inflate into your man cave (negative pressure). Might not appear to be working much with a 130 cfm, if so, block the crack under the door and you should see it inflate.
> 
> Then turn the furnace on. If the bag deflates, you have positive pressure back into the HVAC.
> 
> ...


you just made my head ache:hn


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## Wookieefoot (Dec 26, 2007)

No HVAC register in the room so I shouldn't have smoke creeping around the ducts in the house. Well, Ill try and get her done this week and throw some pics up. Thanks for the feedback! :tu


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## Mark C (Sep 19, 2007)

130 CFM in a room that size, built under normal conditions (meaning you DON'T go to great lengths to seal the room) will not produce any discernible pressure differentials. I'd bet your room will easily leak enough to air to cover that. If your room is surrounded by a conditioned airspace, conditioned air will leak into your room and should keep you comfortable. If it's surrounded by unconditioned space, it could get chilly in the winter time.

At higher flow rates you would see a negative pressure inside your room if it was exhaust-only. This would be a good thing because it would trap all the smoke in your room and ensure none of it leaks into the surrounding area, then exhaust it all out through your fan. This is one of the underlying principles used in contamination control, whether it be a hospital room, industrial facility, etc. The pressure differential is used to isolate contaminated air from clean areas and filtered/exhausted as necessary.

All fans are rated in CFM at a given pressure differential. If your fan is drawing from a well-sealed room, that will increase the pressure differential across the fan. If you use small ducting, long stretches of ducting, or lots of elbows and bends, you'll add to the pressure differential. The higher the pressure, the harder your fan has to work to achieve the desired output, meaning higher power usage. In the case of your bathroom exhaust fan, it will likely decrease the CFM output of the fan, rather than increasing the power load.

Also keep in mind your fan duct will be positively pressurized at the outlet of the fan. This means that if the ductwork leaks, it will send smoke into the surrounding area, wherever your ductwork is run. Maybe not a problem if you've got a straight shot outside, but if you've got to run ducting through a 'clean' part of your house, consider good duct sealing.


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## Bones (Dec 24, 2007)

Wookieefoot said:


> I got tired of standing around in my non-heated garage for an hour+ in this chilly MN weather.


Tell me about it, my last cigar I was outside in the wind just two days ago.

My two friends finished theirs and I had to toss the rest of mine because they got too cold.

Good luck with your cave, and I want to see some pictures when you get it done.


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## Addiction (May 8, 2007)

Da Klugs said:


> 130 cfm is not a large amount of airflow smoke wise. It's probably enough for one smoker. If you have guests it will get hazy. The real issue is your HVAC. If there is a return air duct in your man cave.. it will suck smoke into your HVAC and spread it around the house. I have a 700 cfm fan in my office.. around 25 x 20. It creates "negative pressure" meaning air wants to flow into the room from any point.. cracks in walls, through the door (nice breeze), the cold air return as well as the intake vents from the furnace. But, when the furnace is running the returns go positive meaning that they suck air from my office back into the HVAC stinking up the rest of the office. This is a combination of the increased pressure being added by the HVAC intakes and the returns having more negative pressure at the duct point than the exhaust fan can generate for the entire space. If you have a return in your man cave you can test this by taping a plastic garbage bag around the return vent. with your fan on and the furnace off the bag should partially inflate into your man cave (negative pressure). Might not appear to be working much with a 130 cfm, if so, block the crack under the door and you should see it inflate.
> 
> Then turn the furnace on. If the bag deflates, you have positive pressure back into the HVAC.
> 
> ...


Crap, I'm going to need a drawing to grasp this picture.


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## replicant_argent (May 13, 2006)

I put in a 110 or 130 cfm (or so, can't remember) fan in my office, and it works pretty well, I need to straighten a kink or two in the exhaust run to maximize the cfm, but it works relatively well, I also put an adjustable vaned grate in the return so I can shut it off at will, as well as put a magnetic sheet over it to help stop the HVAC from pulling smoke into the house air. I can crack the window to make up air if needed, but I think I pull a fair amount from under the door.
Yes, Minnesota sucks in the winter for smoking.
Hell, who am I kidding, MN sucks for smoking quite a bit if you want to actually go anywhere, but I am trying to make the best of the situation. Welcome to CS.


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## ZYA_LTR (Oct 15, 2007)

Here, just build one of these:

http://www.ryandeyer.com/cigarroom/index.html


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## Wookieefoot (Dec 26, 2007)

ZYA_LTR said:


> Here, just build one of these:
> 
> http://www.ryandeyer.com/cigarroom/index.html


You don't know how many times I have looked this site over and over and over... I really wanted to go all out like this, but I'm not staying in this home for very long. Wifey and I are gonna sell in a couple years.

On a side note, would a 340 cfm fan make a huge difference over a 110 cfm fan? I went with the 110 because of the 1.1 sone level (sound level), which is so quite you can't even tell its on, lol. But the 340 fan is 6.5, if I remember right. That fan was pretty loud, and ManCave is right below the SleepCave/LoveCave and if I have it running at night I don't wanna bother the wife.

Thanks for all the replies, it's awesome to get some knowledgeable feedback.


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## mitro (Mar 13, 2007)

I've been trying to get approval from the wife to partition off a section of the garage as a mancave (not having any luck). I am looking to have a room about the same size or maybe a little smaller (8'x8') and found this fan.

290 CFM and supposedly 2 sones. Search for the part number on ebay for best prices. Also I plan on having a window in the room and would just crack it when I go in there (and the fan is on) to get return air. Otherwise I would have as much of the room sealed as possible.

However since mine would be in the garage it would not be nearly as critical to keep every last bit of smoke smell in the room.


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## DETROITPHA357 (Jul 8, 2006)

ZYA_LTR said:


> Here, just build one of these:
> 
> http://www.ryandeyer.com/cigarroom/index.html


I've smoked in that room b4&I must say it's very nice. The smoke clears out in .5sec. Very nice Basement and Place to smoke.:tu Again nice job MarkTHS


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## sailchaser (Jun 16, 2007)

If your trying to keep cost down and want to add more draw or pull and you are using 4",6",8" circle ducting and have some space you could use a in line booster fan down the run a Little,this can be hardwire into the same circuit as the bath fan..The are 40-80 bucks depending on size and are available at the local home improvement center in the duct aisle.Good Luck on the project :tu


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## Lionfish (Dec 23, 2007)

Good luck on your cigar room! Dont forget pic's.:ss


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## daniyal (Oct 9, 2007)

You may want to re-think the man cave if you're planning on selling.. save the money and build a bigger, badder man cave in the house you buy next. Unfortunately cigar rooms do nothing but decrease real estate values unless you find a fellow BOTL who can appreciate it.


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## Mark C (Sep 19, 2007)

daniyal said:


> You may want to re-think the man cave if you're planning on selling.. save the money and build a bigger, badder man cave in the house you buy next. Unfortunately cigar rooms do nothing but decrease real estate values unless you find a fellow BOTL who can appreciate it.


Depending on the room, I'll bet it could be converted to a wine cellar, storage room, etc.


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## Wookieefoot (Dec 26, 2007)

I was a little worried about that at first, but when we purchased the house this particular room wasn't listed as one of the bedrooms. It was more of a utility room, the room wasn't even finished, heh. I'm pretty sure it won't be to hard to sell it as a utility room/storage room.


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## Mark THS (Feb 5, 2007)

Mark C said:


> Depending on the room, I'll bet it could be converted to a wine cellar, storage room, etc.


Or a workout room, depending on the size.

Ryan's cigar room would be a perfect spot for a treadmill when/if the time comes to sell. All that ventilation removes the workout-funk in no time :ss


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